This is one of my favorite lunches when it's cold out. Nearly too simple for a recipe.
1 can tuna
a couple of tablespoons mayo, to taste
1 T pickle relish, to taste
2 slices cheese, any sort (pictured above is cheddar and swiss)
2 thick slices of bread
Preheat oven to 400 degrees. Mix tuna, mayonnaise, and pickle relish, to taste. Spoon tuna salad onto bread; put cheese on top. Bake in 400 degree oven until cheese is bubbly and just starting to brown, about 10-15 minutes; bread will be toasted by this point.